Gas Chromatography - Tandem Techniques - Modern GC/IR Systems > Thermogravimetric Analysis (TGA) Coupled with GC/IR and GC/MS > Page 58



Figure 47. The Tube Arrangement of the Valveless Sample Injector

The total system is made solely of fused quartz tubing and the basic tube arrangement is shown in Figure 47. It is seen that the device is easy to construct, simple to operate and can be very compact. The authors demonstrated the use of the total TGA/GC/FTIR/MS apparatus by using it to examine the thermal degradation of poly-(a-methyl styrene), a styrene-isoprene block copolymer, and showed how it could be used to identify the decomposition products. Thermal degradation products could also be examined using the light pipe interface, which although not nearly as sensitive or as fast, would be much less expensive. Furthermore, the light pipe can yield spectral data that is at least as accurate and precise as that obtained from the cryogenic interface. An example of the application of the instrument to the thermal degredation of polythene is as follows. 5 mg of a polyethylene film, 50 mm thick, dispersed on the surface of a platinum coil pyrolysis probe, was placed at the inlet of an open tubular column and heated to a temperature of about 1000ūC for a period of 10 seconds.